I have always eaten the guts/brains. I didn't know there was a risk of ingesting contaminants from their filtration organ. I hope those aquaculture farmers keep their ponds clean.
Any filtration organ is going to be liquefied into nothingness after boiling them for 20 minutes in a giant pot filled with salt, lemon, and garlic, and spices at 300 degrees.
I wouldn't worry. Maybe if you were eating them raw and you ate them a few times a week, but who wants to eat raw crawfish? You could, I suppose. I doubt they'd be very good. Maybe if you survived a plane crash and were stuck in the swamp for a while, and it was a survival situation.
I guarantee boiled crawfish is a whole lot safer than raw sushi though.
If you're eating crawfish that came from Louisiana, and there's a good chance you are as they produce something like 80% of them, there's about a 50% chance that they came from the wild, caught by commercial fishermen as opposed to being farm raised.
Either way, there is oversight in place. There has to be, since most of them are consumed locally and you wouldn't want to make your primary customer base sick.
Something I just looked up:
(LDWF = Louisiana Department of Wildlife and Fisheries)
Wild Crawfish
LDWF is responsible for
monitoring and managing wild crawfish through gear, licensing, and reporting requirements. Harvest controls are not necessary to protect the crawfish resource as their populations are resilient and influenced by environmental conditions, rather than fishing. While biologists conduct studies on wild crawfish, they do not sample and survey the populations like other fishery resources. To monitor wild crawfish harvests, LDWF requires docks that purchase crawfish directly from commercial fishermen to submit
trip tickets to capture information about their catch—what it is, where and how it was caught, etc. Commercial fishermen who sell their catch directly to consumers are also required to complete and submit trip tickets.
Farm-Raised Crawfish
Since farm-raised crawfish are an agricultural product, they fall under the purview of the Louisiana Department of Agriculture and Forestry, the U.S. Department of Agriculture, and other agencies. However, farmers who plan to resell their crawfish must have the appropriate licenses from LDWF and other agencies.